Paraffin removal



atented Nov. H2, 1946 PARAFFIN REMOVAL Delaware Application June 11,1942, Serial No. 446,642

7 Claims. (Cl. 1348) This invention relates to the removal of unwantedsubstances from the inner surface of pipe lines and more particularly toa method and an apparatus for removing wax adhering to the inner surfaceof a pipe line or conduit carrying oil under pressure to a fluidpressure motor. The principal object of the invention is to provide amethod and means for removing a deposit of wax from the inner surface ofa pipe conducting oil under pressure to a pressure motor during normaloperation of the motor and without any detrimental eifect either to theoil being conducted through the pipe or to the mechanism of the motor.

In certain well pumping operations a hydraulic production devicecomprisinga fluid pressure motor connected directly to a pum is placedin the producing zone of a well and the motor is actuated by means ofthe pressure of a liquid such as oil, conducted from a pump at thesurface through a small diameter pipe line or conduit to the motor inthe well. The pressure of the fluid being pumped down to the motorcauses the motor to drive the pump so as to raise the oil from theformation to the surface through .a production tubing string. The pipecarrying the oil under pressure to the motor in the well usually has aninternal diameter of about three-quarters of an inch, and it has beenfound that paraflin frequently accumulates and adheres to the innersurface of this pipe or power tubing thereby decreasing the eillciencyof the system. This is particularly true during hot weather. Variousattempts have been made to develop a satisfactory method for removingthe paraflin from the pipe but these have generally provedunsatisfactory. To remove the power tubing from the well and clean it,as by scraping, requires-that the well be shut down for some time andthis naturally is an expensive operation. Any insoluble body which mightbe forced through the tubing to scrape the paraffin from the innersurface of the pipe would;

of course, cause damage to the motor of the production unit or at leastwould plug the tubing so that .the motor and pump could not be operated.

In accordance with the present invention a method has been devisedwhereby the paramn deposit can be easily removed from the power tubingwithout disassembling the tubing or the production unit and withoutcausing any damage to the mechanism of the motor or'well pump. A solidbody, preferably a sphere, of a substance such as a normally solidhydrocarbon conforming generally in size and shape to the inner contourof the power tubing is placed in the tubing at the under pressure. Ithas been found that a substance of this kind will be dissolved ordisintegrated slowly due to the action of the oil during its passagethrough the tubing. In case the body reaches the motor before it hasbeen completely dissolved it will be held at the intake strainer of themotor and the flow of pressure 011 around and past the body will thendissolve it very quickly. The dissolved body then passes with thepressure oil through the motor and asses with the'oil exhausted from themotor bac to the surface along with the oil being pumped from theproducing formation.

For a better understanding of the invention reference may be had to theaccompanying drawing in which:

Figure 1 is a vertical elevation partly in section through a wellbeingpumped by means of a hydraulic production unit; and

Figure 2 is a vertical sectional elevation through a portion of thepower tubing showing one of the bodies being forced through the tubingto remove the paraflin which has accumulated therein.

Figure 1 shows a well hole Ill drilled into the producing formation l2and provided with a casing it cemented as at I6. A casing head l8 closesthe top of the well and a string of production tubing 20 is shown withinthe hole. A pump anchor 22 is disposed at the lower end of the pro-'duction string 20 and secured to this anchor is a production unit 24which usually comprises a well pump and a fluid pressure motor, thelatter being adapted to be actuated by oil pumped ,downwardly through apower tubing string 26 from a suitstances which might be carried in theoil from entering the motor of the production unit. After passingthrough the motor of the production unit, the oil is exhausted into thelower end of the production string 20 and flows upwardly to thesursurface ,of the power tubing 26 and because of the small diameter ofthis tubing a fairly thin layer of paraffin may be suflicient to cutdown materially the efliciency of the apparatus. In order to remove thisdeposit of paraffin from the inner walls of the power tubing a body 34,preferably spherical, of a normally'solid hydrocarbon is placed in theline of power tubing at the surface and is forced downwardly with theoil under pressure on its way to the production unit 24. The body 34 maybe placed in the power tubing in any suitable manner. A T pipe-fitting36 is shown as connected in the power tubing line and one end of this Tmay be provided with a plug 38 which may be removed so that the ball 34can be placed in the tubing line. As the ball 34- passes through thetubing 26 the paramn 32 is scraped from the walls and passes downwardlyand through the fluid pressure motor of the production unit 24.

It has been found that a ball of naphthalene, such as a commercial mothball, which has a diameter of about five-eighths of an inch serves verysatisfactorily for this purpose. The naphthalene ball will dissolve ordisintegrate gradually in the presence of the oil within the powertubing, and it has been found that in normal operation the ball willfinally disintegrate at about the time it reaches the strainer 30. Ifthe ball has not disintegrated at that time, it will lodge against thestrainer 30 and the disintegration will then take'place much'morerapidly due to the turbulence of the oil flowing past the ball. In caseof a deep hole where it is necessary for the ball to pass through arelatively long string of power tubing, or if for any other reason it isfound that the ball disintegrates or dissolves to a material extentbefore it reaches the strainer 30, a slug of oil saturated withnaphthalene may be placed in the tubing 26 directly behind the ball andthe dissolving action of the oil on the naphthalene ball will thus beretarded to any desired degree.

Although it is preferred to use balls of naphthalene, solid balls ofother compounds having substantially equivalent solubilitycharacteristics may also be used; among these other compounds areacenaphthene, phenanthrene, anthracene, and triphenylmethane. Despitethe fact that it is preferred to use a polycyclic aromatic hydrocarbon,bodies of certain normally solid nonhydrocarbons, such as sulfur, can beused also.

These materials do not cause any detrimental contamination of the oilsince the concentration is so low.

It will be seen that a method has been devised by means of which adeposit of parafiin can be quickly and easily removed from the innersurface of the power tubing during the actual well pumping operation,and, consequently, it is not necessary to shut down the pump and toremove the power tubing so that it can be cleaned. Naturally, nooil-insoluble substance can be used for cleaning a pipe line of thistype since there is no way for such an insoluble body to get out of thepower tubing before it reaches the fluid pressure motor driving the wellpump. AL- though with the apparatus as shown it would be necessary tostop the operation of the pump 28 for a few seconds so that the ball 34can be inserted in the T' 35, any suitable trap device, such, forinstance, as is disclosed in the U. S. Letters without stopping theoperation of the pump 28 and without losing any of the oil.

Although the invention has been described with reference to the cleaningof the power tubing of an oil well production unit, it is believedobvious that the same method can be used in cleaning surface pipe linessuch, for instance, as the line leading from a well head to a run-downtank. Again, the invention is not limited to the removing of paraflinfrom an oil conducting pipe or conduit. In any case, where a relativelysoft deposit of a substance is built up on the inner surface of a fluidconducting pipe, a solid body formed of a. material gradually soluble inthe fluid being conducted could be used to scrape the substance from thewalls of the pipe. The nature of the cleaning or scraping body will de-Patent to Stras'ourg 1,808,870, granted June 9,-

pend, of course, on the material which is to be scraped from the pipewalls, the type of fluid being conducted through the pipe, and thelength of time the body will remain in contact with the fluid.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, but only such limitations should be imposed as areindicated in the appended claims.

We claim:

1. The method of removing paraflin adhering to the inner surface of anoil conducting conduit which comprises forcingthrough said conduit.

with the oil a solid body of naphthalene slightly smaller than the innerdiameter of said conduit, said body of naphthalene being graduallydissolved during its passage through the conduit.

2. The method of removing wax adhering to the'inner surface of an oilconducting conduit which comprises forcing through said conduit with the011 an inflexible body of a normally solid, completely oil-solublehydrocarbon conforming generally in size and shape to the inner contourof said conduit, and immediately following said body with a slug of afluid capable of regarding the dissolving action of the oil on said ody.

3. The method of removing wax adhering to the inner surface of an oilconducting conduit which comprises forcing through said conduit with theoil a solid body of naphthalene slightly smaller than the inner diameterof said conduit, and following said body in its passage through theconduit with a slug of oil saturated with naphthalene.

4. The method of removing wax adhering to the inner surface of a conduitconducting oil under pressure to a fluid pressure motor which comprisesforcing through said conduit with the oil a. solid body of a polycyclic,aromatic hydrocarbon, said body being slightly smaller than the innerdiameter of said conduit and capable of i being gradually completelydissolved by the oil the inner surface of a conduit conducting oil underpressure to the in-take strainer of a fluid pressure motor whichcomprises forcing through said conduit with the oil a spherical bodyslightly smaller than the inner diameter of said conduit and capable ofbeing dissolved by the action of the oil substantially by the time thebody reaches said ln-take strainer.

6. A device for cleaning the inner surface of an oil conduit comprisinga body formed of a solid polycyclic aromatic hyerbon, said body beingslightly smaller in diameter than the inner diameter ofsaid conduit, andmeans for forcing said body through the conduit with said oil to scrapethe inner surface of the conduit.

7. A device for cleaning the inner surface oi an oil conduit comprisinga spherical body of naphthalene slightly smaller in diameter than theinner diameter of said conduit, and means for forcing said body throughthe condultwith' said 011 to scrape the inner surface of the conduit,the arrangement being such that the body will be disintegrated by theaction of the oil during passage through the conduit.

HARVEY 11 1'- LANDRUM. CLAYTON A. BUSTED.

